Figure 4. P₇₀₀ redox kinetics for WT and noALK strains at 20 and 30 C.

Using a JTS-10 spectrophotometer, cell suspensions were dark-adapted and then exposed to a pulse of orange actinic light (to excite both PSII and PSI) for 5 seconds (white bar above panel (A)). The actinic light was then turned off (black bar above panel (A)). During this time-course, measuring flashes of 705 nm light probed the redox state of the P₇₀₀ reaction center of PSI. Data were collected from cells that had been grown at 30 C, then measured at 30 C (panel (A,C)) or shifted to 20 C before measurement (panel (B,D)). Panels C and D show the details of re-reduction of P₇₀₀⁺ in the dark for the experiments in panels A and B, respectively. Inhibitors of linear electron flow (10 μM DCMU, which inhibits transfer from PSII to the quinone pool), and linear + cyclic electron flow (1 μM DBMIB, which blocks cyt b₆f) were added as indicated. Each trace is an average of 3 independent experiments.